Rotary transfer machines are generally controlled with cam mechanisms and were usually constructed for the manufacturing of large batches of the same work piece or family of work pieces which do not differ much from each other. The manual positioning and manual correction of the positioning of machining units mounted on rotary transfer machines is hugely time consuming and very expensive, in particular in cases where a high level of precision is required. The flexibility and the reconfigurability of these machines are therefore limited. However, the simplicity of these machines and their reliability does allow low manufacturing costs and a high inherent availability. Their use requires highly qualified staff with experience and dexterity.
Rotary transfer machines are still manufactured for the machining of work pieces in big batches. In the past few years new rotary transfer machines were developed and produced with machining units equipped with numerical control (CNC). This evolution allows a fast and efficient positioning and correction of the positioning of the machining units regardless of the operator's skills and experience.
However the large number of CNC controlled units causes a significant increase of the construction costs and service costs. The high quantity of electrical devices may increase the probability of default of one of said electrical devices which consequently leads to a decrease of the inherent availability of the machine. Because of the concept of this kind of machines, the downtime of a single station implies the downtime of the entire machine.
For example, EP 1 064 119 (Mikron S. A.) discloses a rotary transfer machine with a stiff base structure and an indexing table comprising a plurality of machining positions. Machining units are coupled to two sides of struts surrounding the indexing table. Each machining unit may be linearly translated about three axes.
JP 4192251 B2 (Seiki Techno Design Co. Ltd.) describes a rotary transfer machine. The body of the machine comprises holes in its sides into which saddles each machining units may be inserted. Each saddle may be moved in the vertical direction by a first servo motor. With a second servo motor each saddle may be moved in a radial direction.
DE 199 58 461 C1 (ESA Eppinger GmbH) discloses a clamping device for machining units, consisting of a platen and a holder. The platen is a regular platen, e.g. a turret. The holder allows to align a machining unit in an external setting system and to keep these alignment settings during storage and transport to a machine. The holder comprises, in addition to a DIN 69880 holder, an adjustment device. The adjustment device comprises two set screws having axes which are parallel to the platen area and which act on a setting bar which abuts onto the platen. With this adjustment device, it is possible to adjust the working axis of the machining unit to be parallel to the working axis of the machine. However, as the alignment relies on the interaction of set screws with a setting bar, the alignment is affected by micro movements.
FR 2 495 978 A (Renault) describes a mounting system for tools. The mounting system comprises an adapter which may be fixed to a shaft of the machine. This mounting system allows a fast change of the tools, as only the adapter has to be initially aligned on an external setting system. A tool holder comprises a special structure with flat nose sections and a channel with which it can be aligned precisely with respect to the adapter.